This is what I call numeracy

From Vasily Grossman‘s notebooks published in A Writer at War, pp. 161-162, an entry about the Red Army infantry fighting off Luftwaffe in Stalingrad:

The brains of the Red Army have finally turned to to the anti-tank rifle … [using] a cart wheel, fastened to a picket and rotating through 360 [degrees]. […]

Battalion Commander Captain Ilgachkin had a problem: he never could manage to hit an aircraft with a rifle. He made theoretical calculations of the speed of bullet from an anti-tank rifle (one thousand meters per second), made a table, supplemented it with information on whether an aircraft is moving towards the firing point or away from it. Having made this table, he hit the aircraft immediately. After that, he fastened a stake in the ground, made an axle, put a wheel on it and they attached an anti-tank rifle to the spokes.

These “theoretical calculations” were made under shell fire in trenches of Stalingrad…